The immune surveillance system provides a host with defense against foreign antigens, but also limits activity against self-antigens thereby preventing autoimmune disease. Cell surface immune checkpoint molecules are endogenous regulators of the immune response which limit autoimmunity by enabling co-inhibitory signaling pathways. Immune checkpoint pathways are important in tumor growth by leading to T-cell depletion and allowing tumors to escape from immune surveillance and enabling unchecked tumor growth. Molecules such as monoclonal antibodies (mAbs) can be designed to target immune checkpoints and such molecules can antagonize co-inhibitory immune pathways, restore immune surveillance, and produce an anti-tumor immune response.
Also, the full anti-tumor effects of immunotherapies can be derived only when they are used in combination with other compounds which can overcome resistance that develop to the immunotherapies by modulating immune pathways.